What stone is it and what’s it worth?

If you are not a jeweller or jewellery specialist, selling your jewellery can be a daunting process. What’s it worth? What gemstone is it? Are the gemstones valuable? Are they even real? These are the most common initial questions you may have when deciding whether to sell your jewellery.

If you were the original buyer of your item of jewellery, you most likely will know the specifics of the gemstone and have a general idea of its value. In the case of antique/vintage jewellery that you may have inherited or bought on the secondary market, there may be a few unknowns. At Sydney Auction House, we specialise in analysing and assessing your items, and will identify the gemstones, and provide an estimate value.

The following is a guide to gemstone identification of faceted transparent stones.



Diamond: Whether it’s a large centre stone, mid-sized shank stone, or small stone, if it’s white/clear, you always hope it’s a Diamond. At Sydney Auction House, we have Diamond Testing Devices to determine whether your stone is a Diamond or not.


Cubic Zirconia: Cubic Zirconia, also known as CZ, is a synthesized material of low cost, and shares a visual likeness to diamond. To the naked and untrained eye, CZ can look very close to the look of a Diamond, which is why it is the main Diamond simulant in the world. We have the relevant devices to test whether your stones are CZ or Diamond.


Moissanite: Moissanite is naturally occurring silicon carbide. Although rare to be found in it’s natural form, Moissanite is widely created in a lab-grown environment and marketed as a positive Diamond alternative as a result of sharing some similar properties to that of Diamonds. As a result of it’s similar optical properties, Moissanite stones are sometimes sold as Natural Diamonds in unassuming scams.


Topaz: Colourless Topaz, also known as White Topaz, is also a cheaper alternative to Diamond. Once cut and faceted, White Topaz can at first glance to the untrained eye, look similar to a Diamond.


Lab Grown Diamond: More popular now than ever, Lab Grown Diamonds are man made Diamonds produced by a controlled technological process, in contrast to Natural Diamonds which are created through geological processes and mined in the natural environment. Lab Grown Diamonds share identical chemical and physical properties to that of Natural Diamonds, making it not only an alternative to Natural Diamonds (sold slightly cheaper), but also the first real competitor in the jewellery industry as we move into a more environmentally conscious marketplace.


Left to right - Ruby, Red Spinel, and Garnet.

Ruby: When you have an unidentified red stone, Ruby is what you hope it to be. Varying from pinkish red to blood red, high quality Rubies are one of the most valued and prized gemstones. With a hardness of 9 on the Mohs scale of hardness, Ruby is very durable. As with all other gemstones, the value of Ruby is determined by it’s colour, cut, clarity, and carat weight. Natural Rubies will generally contain imperfections and inclusions. The clearer the stone, the higher the value, but if it’s too clear with no visible rutile inclusions, this is usually an indication that the stone may be treated, and therefore will reduce the price drastically.


Garnet: As is common with other gemstones, they can come in various colours but there’s generally one colour that precedes the others. Garnet is most known as a red gemstone, but also available in orange, yellow, green, purple, brown, blue, black, pink, and colourless. Due to the vast range of colours, and the fact that Garnet is not a single species, but rather composed of multiple species and varieties, identifying Garnet can be a complex task. Red Garnets tend to be a darker red in comparison to Ruby. A red Garnet will generally be belonging to the mineral species Pyrope, or Almandine. There are beautiful examples of Garnet that produce stunning shades of red which at first glance, may appear as Ruby, but will most likely be a Pyrope Garnet or Almandine Garnet. Garnets are not valued as high as Ruby, and far more accessible due to the lower price point.


The Imperial State Crown featuring a Red Spinel long thought to be a Ruby.

Spinel: Red Spinel has long been an underappreciated gemstone with little to no recognition in the consumer market at large. Only recently, due to the increasing scarcity of Ruby, that demand has increased for this stunning gemstone. Due to their similar appearance, Red Spinels have often been mistaken as Rubies, or at least referred to as Rubies. One particular example is the irregular shaped 170 carat cabochon featured in the Imperial State Crown of the United Kingdom. It’s known as the ‘Black Prince’s Ruby’, being in possession of England’s rulers since 1367. Back in those days, all red gemstones were referred to as Rubies, and it wasn’t until 1783 that Red Spinels were chemically differentiated from rubies.


Fake/glass/paste: Imitated/simulated/fake gemstones are different to synthetic gemstones. Synthetic gemstones are physically, optically, and chemically identical to natural gemstones, but are created in a laboratory. Imitated gemstones are chemically different to natural gemstones but appear visually similar, and are usually made from glass, plastic, and resins, and have no real value.


Left to right - Aquamarine, Cornflower Blue Sapphire, Royal Blue Sapphire, Tanzanite, Blue Spinel.

Sapphire: The most famous of blue gemstones, and the most desirable. Sapphire is also available in many other colours, such as yellow, green, and orange, but it is definitely the blue variety that takes the lead. Sapphire is one of the two gem varieties of the mineral corundum, with the other being Ruby (displayed as red due to presence of the element chromium). Sapphire is available in all shades of blue, with the most valuable and prized being the Royal Blue stones of Kashmir. Australian Sapphires tend to be darker, but still producing beautiful stones, especially the Parti-coloured examples (showing two colours in a single stone, most commonly green and yellow). High quality Ceylon Sapphires, demonstrating the ‘cornflower blue’ are also very prized with the colour being slightly lighter than classic royal blue.


Tanzanite: Relatively speaking, Tanzanite is a very ‘new’ gemstone, first discovered in 1967. Tanzanite is quite unique due to the fact that it is only found in one place in the whole world, Tanzania. Tanzanite is the name assigned to the stone by Tiffany & Co for marketing purposes, but scientifically speaking, this gemstone is the blue and violet variety of the mineral Zoisite. Another beautiful stone, easily identifiable due to the presence of violet/purple, yet sometimes can be mistaken as Sapphire in some instances.

Aquamarine: Easily distinguished from other blue gemstones, Aquamarine is pale blue in colour, reminiscent of the colour of water. Aquamarine’s are available in large sizes.


Blue Spinel: Spinels in general are quite rare in the mainstream jewellery market due to lack of awareness or marketing (and limited supply), but are slowly receiving much deserved recognition due to their unique properties which make them very attractive gemstones for jewellery. Rarer than the red variety, Blue Spinels range in colour from blue-gray to violet-blue, greenish-blue and cobalt blue.


Kyanite: Rarely seen in the mass market, Kyanite is a dark blue gemstone, similar in visual appearance to some varieties of Sapphire. Kyanite is a softer stone, with varying hardness of 4.5-7. When cut and polished, it can produce some exceptional gemstones, although due to the ‘semi-precious’ classification, do not have a particularly high value in the retail market.





Left to right - Green Sapphire, Tsavorite, Emerald, Australian Parti Sapphire, Peridot.

Emerald: Much like Ruby for red, and Sapphire for blue, the king of green gemstones is undoubtedly Emerald. As with all other gemstones, Emeralds can vary greatly in size and quality, and stones of a high quality can be incredibly valuable. Emerald is a variety of the mineral beryl (other varities of beryl are aquamarine and morganite), and coloured green by trace amounts of chromium and in some instances vanadium. In comparison to Sapphire and Ruby, Emerald is a softer stone (7.5 to 8 hardness on the Mohs scale), and highly included, therefore making clear stones exceptionally rare. As a result, if you come across a green gemstone that looks like Emerald but has great clarity, it’s most likely a synthetic or imitation stone.


Synthetic Emerald: Synthetic Emeralds go by many names (generally depending on the laboratory which made them), but the most popular names you may hear are Gilson Emerald, Chatham Emerald, or Hydrothermal Emerald. These are lab grown Emeralds which have the same chemical, physical, and optical properties as a natural Emerald. Unlike natural Emeralds, synthetic Emeralds do not contain any inclusions or imperfections which makes them quite easy to identify.

Green Sapphire: Although Sapphire is synonymous with blue, the popular gemstone is available in a range of greens, of various shades. Green Sapphires are easily identified and will never be mistaken for an Emerald. Australia produces large amounts of Green Sapphires, ranging from quite dark to light and bright varieties, as well as the much loved ‘Parti Sapphire’, which is predominantly a blend of green and yellow.


Tsavorite: You could argue that Tsavorite demonstrates a green colour more similar to that of Emerald than any other green gemstone. Gemstones of high quality and size can fetch very high prices, but gemstones of smaller sizes and average quality are quite accessible. Much like Tanzanite, Tsavorite is a recently ‘new’ gemstone, having only been discovered in 1967 in Tanzania, and first marketed and retailed through Tiffany & Co. On a scientific note, Tsavorite actually belongs to the Garnet group of species, and coloured green as a result of trace amounts of vanadium or chromium, just like Emerald.


Peridot: Belonging to the mineral species Olivine, Peridot is one of the only gemstones which occurs in only one colour. Most examples of this gemstone are ‘apple green’ or ‘olive green’. The intensity of the green depends on the percentage of iron present in the crystal structure.